To test safety of a vehicle, automobile companies and research institutes perform a safety test. In particular, researches for minimizing bad effects on passengers by simulating situations occurring due to a crash accident of a vehicle in advance have been conducted.
As a plan of the research, a crash test process for testing how passengers are affected at the time of the occurrence of a safety accident is essentially performed when car makers develop new cars.
In the crash test process, a dummy is placed inside a vehicle which is an object of a crash test and then the vehicle collides with a crash member, and the like at various speeds, and as a result a shock applied to the dummy is measured by a meter such as a sensor or is photographed as an image to be analyzed.
However, the crash test process is accompanied by a long preparation process due to the preparation of a plurality of actual vehicles meeting speed conditions for testing, the preparation of dummies meeting conditions in vehicles, and the like and therefore is quite expensive to use vehicles for the tests, in addition to a long investment period. As a result, the crash test process may cause temporal and human losses.
To solve the above problem, a crash test of a vehicle is performed under the same environment as the actual accident by installing an accelerated actuator for test in the vehicle and applying an accelerating force generated by a pressure fluid to a tested vehicle or a tested object meeting conditions through a piston and a rod within the actuator.
U.S. Pat. No. 8,453,489 (Registered on Jun. 4, 2013 entitled “Method and System for Concluding Crash Tests”) proposed a method and a system for performing a crash test applying a shock to a targeted object by operating a piston and a rod by a pressure fluid.
The actuator used for the above-mentioned crash test and the general crash test includes a shock absorbing apparatus to prevent an internal shock between the piston and a body of the actuator occurring due to a malfunction of the actuator during the crash test.
The general shock absorbing apparatus having elasticity is included in the actuator and therefore the actuator in which the piston and the rod are progressed in a stroke direction at a rapid speed is hard to absorb a shock and the actuator and the shock absorbing apparatus are applied with a pressure generated by the shock and are thus likely to be damaged.
As another method, there is a method for absorbing a shock generated by a malfunction using a crush tube, etc.
However, the crush tube is a disposable product and therefore the crush tube is dented by a shock needs to be replaced, which leads to a problem in that additional costs and maintenance time are required every time the crush tube is replaced.